Electrical connector

ABSTRACT

An electrical connector in which a free end of a leaf spring is located close to a supporting wall, and a wire lead is wedged in between the support and spring. The other end of the spring is soldered to a printed circuit board. Loosening or damage to the solder point is prevented on lead insertion or removal or attempted removal by wedging the free end between the lead and the board itself. The said other end of the spring has two spaced tabs which project through two holes, respectively, in the board. The tabs are tapered and take the lead insertion load without loading solder joints between the tabs and the board. The two tabs also give the spring lateral stability.

United States Patent J ulinot 51 Mar. 7, 1972 [54] ELECTRICAL CONNECTOR 21 Appl. No.: 67,420

[30] Foreign Application Priority Data May 19, 1970 Canada ..083059 [52] US. Cl. ..339/17 R, 174/68.5, 324/158 F,

339/95 D, 339/210, 339/275 B [51] Int. Cl. ..l-l0lr 11/20, H05k 1/02 [58] Field of Search ..l74/68.5, 94; 339/17 RC, 17 N,

339/17 F, 17 D, 17 M, 17 L, 17 LC, 18 R, 18 C, 18.

P, 19, 28, 61, 65, 74, 95 R, 95 D, 103, 105, 119,

149 P, 175 R, 175 C, 176 R, 176 MP, 198 R, 198 E, 198 K, 198 N, 206 R, 207 R,-207 S, 210, 216, 221, 241, 244, 252, 256, 258, 273, 275 R, 275 B, 277,

Sanders, .lr ..339/17 LM 3,059,152 '10/1962 Khouri ..339/275 B X FOREIGN PATENTS OR APPLICATIONS 751,675 7/1956 Great Britain .339/95 D Primary Examiner-Marvin A. Champion Assistant Examiner-Terrell P. Lewis Attorney-C. Cornell Remsen, .lr., Walter J. Baum, Paul W. Hemminger, Charles L. Johnson, Jr. and Thomas E. Kristoffe'rson [5 7] ABSTRACT An electrical connector in which a free end of a leaf spring is located close to a supporting wall, and a wire lead is wedged in between the support and spring. The other end of the spring is soldered to a printed circuit board. Loosening or damage to the solder point is prevented on lead insertion or removal or attempted removal by wedging the free end between the lead and the board itself. The said other end of the spring has two spaced tabs which project through two holes, respectively, in the board. The tabs are tapered and take the lead insertion load without loading solder joints between the tabs and the board. The two tabs also give the spring lateral stability.

13 Claims, 6 Drawing Figures PATENTEDHAR 7 I972 INVENTOR. HEM/107 D. (/UL/A/OT HTTOR/VEY ELECTRICAL CONNECTOR BACKGROUND OF THE INVENTION This invention relates to devices for making connection with, for example, solid or stranded, cylindrical conductive lead and some other conductor, and more particularly to a quick detachable electrical connector for a printed circuit board or the like, and a printed circuit board junction therefor.

In the past it has been the practice to provide a leaf spring conductor with a free end adjacent a wall between which a wire is inserted to make contact. The free end of the spring is spaced a distance from the wall less than the wire diameter so that the wire is held by the bite thereon of the spring.

Such a prior art device is disclosed in US. Pat. No. 2,952,831. This device is extremely useful in applications where rapid insertion and immediate wire retention are desired. Even so, this device may be easily released by deflecting the spring in the proper direction.

The said prior art device would be of enormous utility as a printed circuit board connector because of the large number of connectors which are required for such a board. However, to the present time no practical prior art device has been devised because when the spring is soldered to the board, the solder joint is stressed on lead insertion, removal or when the lead is pulled outwardly in the direction of removal without freeing the spring from the lead. This stress either causes th solder joint to become loose, damaged or broken.

SUMMARY OF THE INVENTION In accordance with the device of the present invention, the above described and other disadvantages of the prior art are overcome by providing an improved leaf spring connector for an electrical lead in which all or a portion of the forces transmitted by the spring are opposed by a structure other than the solder joint. The solder joint is thus protected and is not damaged or broken even through the leaf spring is soldered directly to the board.

Another independent feature of the invention is the use of two spaced tabs which project through two holes, respectively, in the board. This arrangement provides for structural rigidity when the tabs are soldered to the board. The tabs are also tapered to engage the board holes; whereby the board rather than the solder joints take the stress which would normally be transferred thereto when the spring itself is stressed. The two tabs also give the spring lateral stability.

The above described and other advantages of the invention will be better understood from the following description when considered in connection with the accompanying drawings:

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings, which are to be regarded as merely illustrative:

FIG. 1 is a printed circuit board assembly constructed in accordance with the present invention;

FIG. 2 is a sectional view of the assembly taken on the line 2-2 shown in FIG. 1;

FIG. 3 is a sectional view of the assembly taken on the line 3-3 shown in FIG. 2;

FIG. 4 is a sectional view of a printed circuit board connection of the present invention alternative to that shown in FIG.

FIG. 5 is a sectional view of still another alternative embodiment of the invention; and

FIG. 6 is a sectional view of the arrangement shown in FIG. 5 taken on the line 66 therein.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. I a printed circuit board assembly is indicated at 10 including a housing 11 having end sections 12 and 13, and side sections 14 and 15. Housing 11 may or may not have a rectangular bottom panel, not shown, if desired.

A printed circuit board 16, as will be described, may be slidable into housing 11 upon assembly and fixed or not thereto, if desired. Printed circuit board 16 has a conductive strip 17. Strip 17, by itself, may or may not be fixed to board 16, as desired. It will be noted that printed circuit board 16 may carry a great many conductive strips 17, although only one such conductive strip 17 is illustrated. 1

As will be described, printed circuit board 16 and strip 17 may have two registering holes, not shown in FIG. 1, through which two conductive tabs 18 and 19 project, respectively. Conductive tab 18 is conductively bonded to strip 17 by solder at 20. Conductive tab 19 is conductively bonded to strip 17 by solder at 21. Counter sunk holes 22 and 23 are provided through housing wall 15.

Tab 18 is shown in both FIGS. 2 and 3, Tab 17 is also shown in FIG. 3. The hole through board 16 through which tab 18 projects is indicated at 24. The hole in strip 17 through which tab 18 projects is indicated at 25. Holes 24 and 25 may lie in registration, as shown. These holes may be circular, rectangular, or of any other suitable cross section.

As shown in FIGS. 2 and 3, tabs 18 and 19, if desired, may be soldered to strip 17 while a cutout portion 26 of a conductive leaf spring metal strip 27 engages the sharp edges 28 and 29 of both holes 24 and 30.

As shown in FIG. 2, strip continues around a bracket 31 to a position near a substantially flat horizontal surface 32 which supports a solid or braided conductor 33 of circular cross section. Conductor 33 is a part of alead 34 having insulation at 35. Conductor 33 is slidable through hole 23.

Depending upon which of the features of the invention are to be practiced, board 16 may be slidable, withone or more springs 27 attached into the space between wall 15 and bracket 31. Bracket 31 is fixed to wall 15. The fit of spring 27 and board 16 between bracket 31 and wall 15 may be quite tight, snug or slightly loose, whichever is desired. If desired, board 16 may be fixed to wall 15.

Spring 27, except for the end portion thereof at and above cut out 26 shown in FIG. 3, may have a uniform rectangular cross section throughout its entire length. Note will be taken that the thickness of spring 27 is substantially smaller than its width.

As viewed in FIG. 2, the extreme lower end of spring 27 has a rectangular end surface lying in a plane substantially perpendicular to the length of the lower end. The extreme lower end of spring 27, shown in FIG. 2, thus has a sharp corner at 36 to cut into conductor 33 and thereby prevent the removal of conductor 33 to the right, as viewed in FIG. 2.

Bracket 31 may have a uniform cross section throughout its length. This cross section is shown in FIG. 2. Bracket 31 may have a length, if desired, only slightly less than the length of wall 15.

OPERATION Insertion In operation, before conductor 33 is inserted inside housing 11, spring 27 may take the position indicated at 27' in dotted lines in FIG. 2. In the position 27', spring 27 may be unstressed. In this position, spring edge 36 is now at 36. Note that 36 is located from surface 32 a distance less than the diameter of conductor 33. This means that when conductor 33 is inserted, as shown, spring 27 will flex and be stressed. During such flexure, note that the solder connections 20 and 21 shown in FIG. 3 will not be substantially stressed because even though the said flexure will tend to cause, by the moment created, the movement of tabs 18 and 19 upwardly in holes 24 and 30 respectively, such movement will not take place because spring 27 engages board 16 at points 28 and 29. Note also that board 16 takes some of the force as well at 37. Movement of tabs 18 and 19 is further retarded thereby.

A'IIEMP'IED REMOVAL WlTI-IOUT SPRING 27 RELEASED Once conductor 33 has been inserted as shown in FIG. 2, any attempt at removal of conductor 33 to the right without release of spring 27 will be resisted by the bite put upon conductor 33 by the sharp edge 36 of spring 27. Moreover, the forces will be such, as will be described, so as to not stress the solder joints 20 and 21 substantially, In particular, the spring 27, as will be noted, is formed substantially in the shape of a U," although the end portion thereof near tabs 18 and 19 is curved into holes 24 and 30. Due to the fact that the leg of the U," which is lower most in FIG. 2, is substantially flat and straight, it tends to remain substantially flat and straight because it is located near the vertical. Moreover, as the force to retract conductor 33 is increased without releasing spring 27, the angle that the lower spring leg makes with surface 32 will increase toward 90. This means that there will be a component of force created by the attempted removal of conductor 33 which is normal to the lower surface of board 16 at 37. This component will be far greater than any other component. That is to say, printed circuit board, on attempted removal of conductor 33, takes most of the reaction force at point 37. The solder joints 20 and 21 are subject to only a small force, if any. Note too that the lower end of spring 27 is loaded primarily as a column on attempted withdrawal without the release of spring 27. The said lower portion will thus be very stiff and transmit all or most all of the load directly to board 16 rather than to solder joints 20 and 21. Note further that the insertion of conductor 31 causes spring 27 to urge projections 18 and 19 upwardly through holes 24 and 30 shown in FIG. 3. This means that an attempted withdrawal and partial movement of conductor 33 to the right in FIG. 2 will only tend to return spring 25 to position 27 where, were the conductor 33 not inserted, there would be no stress tending to move projections 18 and 19 in any direction, i.e., either up or down in holes 24 and 30.

To say it another way, once conductor 33 is inserted, there is a force tending to cause projections 18 and 19 to rise. Thus, some movement of conductor 33 in the direction of withdrawal may only relieve such initial stress and not downwardly pull projections 18 and 19 with any finite force.

In accordance with the foregoing, the device of the present invention can relieve the solder joint stress, and some cases will completely eliminate it.

FIRST ALTERNATIVE EMBODIMENT Although the embodiment of the present invention illustrated in FIGS. 1, 2 and 3 is preferred over all other embodiments disclosed herein, one additional embodiment is disclosed in FIG. 4, and another in FIGS. and 6.

In FIG. 4 a spring is indicated at 38 having a tab 39 soldered at 40 to a conductive strip 41 on a printed circuit board 42. The embodiment of FIG. 4 may be identical to that shown in FIGS. 1, 2 and 3, except that only one hole is provided in conductor 41 and board 42, and only one tab 39 is provided on spring 38.

Note will be taken that the embodiment of FIG. 3 has an advantage over the embodiment shown in FIG. 4. Springs 27 and 38 are relatively long and thin in comparison to their widths. Thus, preferably spring 27 and 38 have a need for lateral stability. This stability is provided by tabs 18 and 19 which are spaced across the width of spring 27 as far as possible.

SECOND ALTERNATIVE EMBODIMENT -The second alternative embodiment is shown in FIG. 5 including a printed circuit board 43 with a conductor 44 thereon, an assembly wall 45, and a bracket 46. A spring 47 over a portion 48 thereof may be identical to a similar portion of spring 27, if desired.

Board 43 may be identical to board 42. Strip 44 may be identical to strip 41. Bracket 46 may be identical to bracket 41. Wall 45 may be identical to wall 15.

All of the printed circuit boards may be made of an insulating material such as plastic. This same is true of all brackets and walls. Printed circuit board 43 also may, as shown, have flat upper and lower surfaces, and have a uniform thickness throughout its extent.

Spring 47 may have a unifonn rectangular cross section throughout its entire length. Note that spring 47 has a portion 49 which lies perfectly flat with the lower surface of board 42. Spring 47 has a right-angle bend at 50 to form a tab 51 which is soldered at 52 to strip 44 as before. f

In the embodiment shown in FIG. 5, note will be taken that there is no stress on solder joint 52 when a conductor is inserted through wall hole 53 between bracket 46 and the lower end of spring 47. This is true because spring portion 49 lies flat against the lower surface of board 43. Again, upon removal of a conductor from between spring 47 and bracket 46, the upper end of portion 48 will tend to wedge against the lower surface of board 43 and any movement of tab 51 downwardly will be minimized or limited.

In accordance with the foregoing, the leaf spring type of electrical connector can, for the first time, be employed and directly connected, i.e., soldered, to a printed circuit board.

It is an advantage of the invention that conventional soldering may be employed.

It is also an advantage of the invention that any tool having an appropriate projection such as the shaft of a miniature screw driver may be inserted through hole 22 in FIG. 2 to push the lower end of spring 27 upwardly to release conductor 33.

It is an advantage of the invention that any pull on conductor 33 only serves to wedge the conductor 33 in securely between the lower end of spring 27 and bracket 31 shown in FIG. 2.

A further advantage of the invention is that the reaction force of the attempted withdrawal of conductor 33 always places spring 27 against board 16 at point 37 where the major forces both of insertion, withdrawal and attempted withdrawal without the release of the spring are taken by the board 16 and not the solder joints 20 and 21.

A further feature of the invention resides in the fact that any upward forces exerted by spring 27 on board 16 at the positions of solder joints 20 and 21 are born at points 28 and 29, and not by the soldered joints themselves.

Another reason why the embodiment shown in FIG. 2 is preferred over that shown in FIG. 5 is that the curve of spring 27 near tabs 18 and 19 is preferred because it makes production of the spring easier and lessexpensive.

As stated previously, any number of terminals can be arranged side by side along an axis perpendicular to the plane of the drawing in FIG. 2. I

Board 16 with its attached springs can be slidably moved in and out of housing 11 along the same axis without disturbing previously made permanent solder connections.

One or any number of springs 27 may be inserted in a printed circuit board upon assembly in the same manner as other electronic components and can be soldered in one operation by means of wave soldering or similar techniques.

Another feature of the invention is that the terminals described above can handle both solid and stranded wires of surprisingly wide ranges of diameters.

Still further, note will be taken that the outside of housing 1 1 presents a smooth and uncluttered appearance.

Although different component parts of the invention have been described as separate, it is to be understood that, for example, the plastic parts may be molded integrally with one another as well as separately.

Although brackets 31 and 46 are believed to be important to hold springs 27 and 47, respectively, contiguous to boards 16 and 43, respectively, brackets 31 and 46 may be omitted in certain instances. Brackets 31 and 46 may be omitted when board 16 and 43 are fixed to walls 15 and 45, respectively. Further, if desired, brackets 31 and 46 may be located in positions sufficiently close to boards 16 and 43, respectively, such that springs 27 and 47 are held in light or substantial compression against the lower surfaces of boards 16 and 43, respectively. Alternatively, with no conductor 33 or the like inserted in holes 23 and 53, springs 27 and 47 may be completely unstressed prior to insertion, if desired, by spacing brackets 31 and 36 a sufficient distance away from board 16 and 43.

What is claimed is:

1. An electrical connector comprising: a conductive U- shaped leaf spring having a fixed end and a free end; a first support, said fixed end being fixed relative to said first support; a second support having a first surface to allow movement of a conductive projection thereon between said first surface and said free end, said first support being substantially fixed relative to said second support, means providing a second surface approximately parallel to said first surface for engagement with said spring on the outside of the U and on the half thereof opposite from that on which said free end is located, said free end being located closer to said first surface than a cross-sectional dimension of said conductive projection when said spring is unstressed, said spring being stressed when said projection is inserted between said free end and said first surface, said conductive projection being insertable in a direction approximately in a plane parallel to the plane of the U, said free end being disposed at an acute angle relative to said first surface when said conductive projection is inserted between said free end and said first surface, said free end extending toward said first surface in the direction of insertion when said conductive projection is inserted between said free end and said first surface, said spring being a strip of conductive metal having a substantially uniform rectangular cross section throughout its length, said strip having a thickness substantially smaller than its width, and a width substantially smaller than its length, said strip being defined between two parallel surfaces having a width equal to the width of said strip, each parallel surface being defined by a line segment moved perpendicular to its length, said line segments always lying perpendicular to the same plane, a cross section of said spring in a plane parallel to said same plane always being U- shaped, a major portion of each half of the U being straight near said spring ends, the major portion at said free end being straight to the very end thereof, said free end having a rectangular end surface in a plane perpendicular to said parallel surfaces and to the other surfaces of said strip at said free end thereof, said spring thus providing a sharp edge at said free end to cut into said projection upon attempted withdrawal thereof, said projection having an approximately circular cross section uniform along its length, said first and second surfaces being flat and parallel, a housing fixed relative to said supports, said housing having first and second access holes therethrough, the first above the second, said projection being insertable through said second hole onto said first surface, said projection being releaseable by insertion of a tool into said first hole, said spring having a portion at said fixed end curving in a direction opposite that of the base of the U, said first support being a printed circuit board made of an insulating material, said means including an integral portion of said board, said spring being located below said board, said board having a conductor on the upper surface thereof, said board having a pair of space holes therethrough, said fixed end having a tab extending through each hole, said tabs being defined on opposite sides of a curved cut out portion of said strip, said pair of holes extending vertically through said board with uniform cross section, said board having flat, parallel upper and lower surfaces, said cut out having a width smaller than the minimum distance between said pair of holes, the curve of said strip at said cut out resting at substantially one point at the edge of each of said pair of holes, said conductor having two spaced holes in registration with said pair of holes, respectively, said tabs projecting through said conductor holes above said conductor, solder bonding both of said tabs to said conductor, and a pointed extension inside the U near the bottom thereof to hold said spring contiguous to said board, said extension being made of an insulating material, said extension being substantially fixed relative to said means.

2. An electrical connector comprising: a conductive U- shaped leaf spring having a fixed end and a free end; a first support, said fixed end being fixed relative to said first support; a second support having a first surface to allow movement of a conductive projection thereon between said first surface and said free end, said first support being substantially fixed relative to said second support, means providing a second surface approximately parallel to said first surface for engagement with said spring on the outside of the U and on the half thereof opposite from that on which said free end is located, said free end being located closer to said first surface than a cross-sectional dimension of said conductive projection when said spring is unstressed, said spring being stressed when said projection is inserted between said free end and said first surface, said conductive projection being insertable in a direction approximately in a plane parallel to the plane of the U, said free end being disposed at an acute angle relative to said first surface when said conductive projection is inserted between said free end and said first surface, said free end extending toward said first surface in the direction of insertion when said conductive projection is inserted between said free end and said first surface, and a nonconductive projection located inside the U to hold said spring contiguous to said second surface, said nonconductive projection being substantially fixed relative to said means, said spring having two legs and a curved bight portion connecting said legs, said spring ends being positioned at the ends of said legs, respectively,'

said nonconductive projection being positioned to contact said bight portion inside the U.

3. The invention as defined in claim 2, wherein said first and second surfaces are substantially flat and parallel.

4. An electrical connector comprising: a conductive U- shaped leaf spring having a fixed end and a free end; a first support, said fixed end being fixed relative to said first support; a second support having a first surface to allow movement of a conductive projection thereon between said first surface and said free end, said first support being substantially fixed relative to said second support, means providing a second surface approximately parallel to said first surface for engagement with said spring on the outside of the U and on the half thereof opposite from that on which said free end is located, said free end being located closer to said first surface than a cross-sectional dimension of said conductive projection when said spring is unstressed, said spring being stressed when said projection is inserted between said free end and said first surface, said conductive projection being insertable in a direction approximately in a plane parallel to the plane of the U, said free end being disposed at an acute angle relative to said first surface when said conductive projection is inserted between said free end and said first surface, said free end extending toward said first surface in the direction of insertion when said conductive projection is inserted between said free end and said first surface, said first support being a printed circuit board made of an insulating material, said board having a hole therethrough, said fixed end having a connecting tab projecting into said hole, said strip having a width greater than that of said hole to limit movement of said tab thereinto, said board lying in a plane approximately parallel to that of said first surface at the position of said second surface.

5. The invention as defined in claim 4, wherein said board has a conductor thereon on the side thereof opposite the side on which said spring is located, said tab being conductively bonded to said conductor.

6. The invention as defined in claim 5, wherein said conductor has a hole therethrough in registration with said board hole.

7. An electrical connector comprising: a conductive U- shaped leaf spring having a fixed end and a free end; a first support, said fixed end being fixed relative to said first support; a second support having a first surface to allow movement of a conductive projection thereon between said first surface and said free end, said first support being substantially fixed relative to said second support, means providing a second surface approximately parallel to said first surface for engagement with said spring on the outside of the U and on the half thereof opposite from that on which said free end is located, said free end being located closer to said first surface than a cross-sectional dimension of said conductive projection when said spring is unstressed, said spring being stressed when said projection is inserted between said free end and said first surface, said conductive projection being insertable in a direction approximately in a plane parallel to the plane of the U, said free end disposed at an acute angle relative to said first surface when said conductive projection is inserted between said free end and said first surface, said free end extending toward said first surface in the direction of insertion when said conductive projection is inserted between said free end and said first surface, said first support being a printed circuit board made of an insulating material, said board having two spaced holes therethrough, said fixed end having a tab at each edge of said spring, said tabs projecting into said holes, the space between tabs increasing away from said free end to beyond the minimum spacing between said holes to limit movement of said tabs into said holes, said board lying in a plane approximately parallel to that of said first surface at the position of said second surface.

8. The invention as defined in claim 7, wherein said board had a conductor thereon on the side thereof opposite the side on which said spring is located, at least one of said tabs being conductively bonded to said conductor.

9. The invention as defined in claim 8, wherein said conductor has one hole in registration with the board hole through which said one tab projects.

10. The invention as defined in claim 9, wherein said conductor has another hole in registration with the board hole through which the other tab projects, both of said tabs being conductively bonded to said conductor.

11. An electrical connector comprising: a conductive U- shaped leaf spring having a fixed end and a free end; a first support, said fixed end being fixed relative to said first support; a second support having a first surface to allow movement of a conductive projection thereon between said first surface and said free end, said first support being substantially fixed relative to said second support, means providing a second surface approximately parallel to said first surface for engagement with said spring on the outside of the U and on the half thereof opposite from that on which said free end is located, said free end being located closer to said first surface than a cross-sectional dimension of said conductive projection when said spring is unstressed, said spring being stressed when said projection is inserted between said free end and said first surface, said conductive projection being insertable in a direction approximately in a plane parallel to the plane of the U, said free end being disposed at an acute angle relative to said first surface when said conductive projection is inserted between said free end and said first surface, said free end extending toward said first surface in the direction of insertion when said conductive projection is inserted between said free end and said first surface, said first support including a printed circuit board, said board including said means as an integral portion thereof, one surface of said board being fiat, and one surface being said second surface, said board being made of an insulating material, said board having a hole therethrough perpendicular to said one surface a substantial portion of said spring lying in contact with said one surface and terminating with a right angle bend with a tab extending into said hole at the said fixed end of said spring.

12. The invention as defined in claim 11, wherein said board has a conductor thereon on the side thereof opposite the side on which said spring is located, said tab being conductively bonded to said conductor.

13. The invention as defined in claim 12, wherein said conductor has a hole therethrough in registration with said board hole. 

1. An electrical connector comprising: a conductive U-shaped leaf spring having a fixed end and a free end; a first support, said fixed end being fixed relative to said first support; a second support having a first surface to allow movement of a conductive projection thereon between said first surface and said free end, said first support being substantially fixed relative to said second support, means providing a second surface approximately parallel to said first surface for engagement with said spring on the outside of the U and on the half thereof opposite from that on which said free end is located, said free end being located closer to said first surface than a crosssectional dimension of said conductive projection when said spring is unstressed, said spring being stressed when said projection is inserted between said free end and said first surface, said conductive projection being insertable in a direction approximately in a plane parallel to the plane of the U, said free end being disposed at an acute angle relative to said first surface when said conductive projection is inserted between said free end and said first surface, said free end extending toward said first surface in the direction of insertion when said conductive projection is inserted between said free end and said first surface, said spring being a strip of conductive metal having a substantially uniform rectangular cross section throughout its length, said strip having a thickness substantially smaller than its width, and a width substantially smaller than its length, said strip being defined between two parallel surfaces having a width equal to the width of said strip, each parallel surface being defined by a line segment moved perpendicular to its length, said line segments always lying perpendicular to the same plane, a cross section of said spring in a plane parallel to said same plane always being Ushaped, a major portion of each half of the U being straight near said spring ends, the major portion at said free end being straight to the very end thereof, said free end having a rectangular end surface in a plane perpendicular to said parallel surfaces and to the other surfaces of said strip at said free end thereof, said spring thUs providing a sharp edge at said free end to cut into said projection upon attempted withdrawal thereof, said projection having an approximately circular cross section uniform along its length, said first and second surfaces being flat and parallel, a housing fixed relative to said supports, said housing having first and second access holes therethrough, the first above the second, said projection being insertable through said second hole onto said first surface, said projection being releaseable by insertion of a tool into said first hole, said spring having a portion at said fixed end curving in a direction opposite that of the base of the U, said first support being a printed circuit board made of an insulating material, said means including an integral portion of said board, said spring being located below said board, said board having a conductor on the upper surface thereof, said board having a pair of space holes therethrough, said fixed end having a tab extending through each hole, said tabs being defined on opposite sides of a curved cut out portion of said strip, said pair of holes extending vertically through said board with uniform cross section, said board having flat, parallel upper and lower surfaces, said cut out having a width smaller than the minimum distance between said pair of holes, the curve of said strip at said cut out resting at substantially one point at the edge of each of said pair of holes, said conductor having two spaced holes in registration with said pair of holes, respectively, said tabs projecting through said conductor holes above said conductor, solder bonding both of said tabs to said conductor, and a pointed extension inside the U near the bottom thereof to hold said spring contiguous to said board, said extension being made of an insulating material, said extension being substantially fixed relative to said means.
 2. An electrical connector comprising: a conductive U-shaped leaf spring having a fixed end and a free end; a first support, said fixed end being fixed relative to said first support; a second support having a first surface to allow movement of a conductive projection thereon between said first surface and said free end, said first support being substantially fixed relative to said second support, means providing a second surface approximately parallel to said first surface for engagement with said spring on the outside of the U and on the half thereof opposite from that on which said free end is located, said free end being located closer to said first surface than a cross-sectional dimension of said conductive projection when said spring is unstressed, said spring being stressed when said projection is inserted between said free end and said first surface, said conductive projection being insertable in a direction approximately in a plane parallel to the plane of the U, said free end being disposed at an acute angle relative to said first surface when said conductive projection is inserted between said free end and said first surface, said free end extending toward said first surface in the direction of insertion when said conductive projection is inserted between said free end and said first surface, and a nonconductive projection located inside the U to hold said spring contiguous to said second surface, said nonconductive projection being substantially fixed relative to said means, said spring having two legs and a curved bight portion connecting said legs, said spring ends being positioned at the ends of said legs, respectively, said nonconductive projection being positioned to contact said bight portion inside the U.
 3. The invention as defined in claim 2, wherein said first and second surfaces are substantially flat and parallel.
 4. An electrical connector comprising: a conductive U-shaped leaf spring having a fixed end and a free end; a first support, said fixed end being fixed relative to said first support; a second support having a first surface to allow movement of a conductive projection thereon between said first surface and said free end, said first support being substantially fixed relative to said second support, means providing a second surface approximately parallel to said first surface for engagement with said spring on the outside of the U and on the half thereof opposite from that on which said free end is located, said free end being located closer to said first surface than a cross-sectional dimension of said conductive projection when said spring is unstressed, said spring being stressed when said projection is inserted between said free end and said first surface, said conductive projection being insertable in a direction approximately in a plane parallel to the plane of the U, said free end being disposed at an acute angle relative to said first surface when said conductive projection is inserted between said free end and said first surface, said free end extending toward said first surface in the direction of insertion when said conductive projection is inserted between said free end and said first surface, said first support being a printed circuit board made of an insulating material, said board having a hole therethrough, said fixed end having a connecting tab projecting into said hole, said strip having a width greater than that of said hole to limit movement of said tab thereinto, said board lying in a plane approximately parallel to that of said first surface at the position of said second surface.
 5. The invention as defined in claim 4, wherein said board has a conductor thereon on the side thereof opposite the side on which said spring is located, said tab being conductively bonded to said conductor.
 6. The invention as defined in claim 5, wherein said conductor has a hole therethrough in registration with said board hole.
 7. An electrical connector comprising: a conductive U-shaped leaf spring having a fixed end and a free end; a first support, said fixed end being fixed relative to said first support; a second support having a first surface to allow movement of a conductive projection thereon between said first surface and said free end, said first support being substantially fixed relative to said second support, means providing a second surface approximately parallel to said first surface for engagement with said spring on the outside of the U and on the half thereof opposite from that on which said free end is located, said free end being located closer to said first surface than a cross-sectional dimension of said conductive projection when said spring is unstressed, said spring being stressed when said projection is inserted between said free end and said first surface, said conductive projection being insertable in a direction approximately in a plane parallel to the plane of the U, said free end disposed at an acute angle relative to said first surface when said conductive projection is inserted between said free end and said first surface, said free end extending toward said first surface in the direction of insertion when said conductive projection is inserted between said free end and said first surface, said first support being a printed circuit board made of an insulating material, said board having two spaced holes therethrough, said fixed end having a tab at each edge of said spring, said tabs projecting into said holes, the space between tabs increasing away from said free end to beyond the minimum spacing between said holes to limit movement of said tabs into said holes, said board lying in a plane approximately parallel to that of said first surface at the position of said second surface.
 8. The invention as defined in claim 7, wherein said board had a conductor thereon on the side thereof opposite the side on which said spring is located, at least one of said tabs being conductively bonded to said conductor.
 9. The invention as defined in claim 8, wherein said conductor has one hole in registration with the board hole through which said one tab projects.
 10. The invention as defined in Claim 9, wherein said conductor has another hole in registration with the board hole through which the other tab projects, both of said tabs being conductively bonded to said conductor.
 11. An electrical connector comprising: a conductive U-shaped leaf spring having a fixed end and a free end; a first support, said fixed end being fixed relative to said first support; a second support having a first surface to allow movement of a conductive projection thereon between said first surface and said free end, said first support being substantially fixed relative to said second support, means providing a second surface approximately parallel to said first surface for engagement with said spring on the outside of the U and on the half thereof opposite from that on which said free end is located, said free end being located closer to said first surface than a cross-sectional dimension of said conductive projection when said spring is unstressed, said spring being stressed when said projection is inserted between said free end and said first surface, said conductive projection being insertable in a direction approximately in a plane parallel to the plane of the U, said free end being disposed at an acute angle relative to said first surface when said conductive projection is inserted between said free end and said first surface, said free end extending toward said first surface in the direction of insertion when said conductive projection is inserted between said free end and said first surface, said first support including a printed circuit board, said board including said means as an integral portion thereof, one surface of said board being flat, and one surface being said second surface, said board being made of an insulating material, said board having a hole therethrough perpendicular to said one surface a substantial portion of said spring lying in contact with said one surface and terminating with a right angle bend with a tab extending into said hole at the said fixed end of said spring.
 12. The invention as defined in claim 11, wherein said board has a conductor thereon on the side thereof opposite the side on which said spring is located, said tab being conductively bonded to said conductor.
 13. The invention as defined in claim 12, wherein said conductor has a hole therethrough in registration with said board hole. 